Triboelectrification is the transfer of electric charge, by contact or by friction, between pieces of different, polymeric materials. Materials may be approximately ranked on a "Triboelectric scale" regarding their tendency give or receive electrons, i.e., become positively or negatively charged. Such scales vary somewhat by researcher and method, but generally tend to agree. The combination of dissimilar, usually fibrous, materials to create a triboelectric enhancement of air filtration media is known in prior art. On contact of polymers having different tendencies to give or receive electrons, localized electrical charges accumulate. These local electric fields aid in capturing airborne particles and make a blend of dissimilar materials useful as air filters. One such filter, described in British Patent 384052 comprises wool fibers and resin particles. A combination of clean fibers of polyolefin and clean fibers of a polymer consisting of one or more halogen or --CN substituted hydrocarbons is described in Brown U.S. Pat. No. 4,798,850.
In an article "Generation of Triboelectric Charge In Textile Fiber Mixtures and Their Use as Air Filters" from the Journal of Electrostatics, volume 21 (1988), pages 81-98, other fibrous polymers were mixed and tested for their triboelectric effect. The article states that many yarns of different types were tested, the best was found to be a combination of polypropylene with modacrylic fibers and is the one also exemplified in U.S. Pat. No. 4,798,850.
Fiber mixtures of ordinary polytetrafluoroethylene (PTFE) and glass fibers available commercially and are known to have triboelectric properties. Fibers of ordinary PTFE are commonly made by mixing a dispersion of PTFE particles in water with a cellulosic binder, forcing the dispersion through a spinnerette, and heating the resulting fiber until the PTFE particles become sintered together and the cellulose largely burned away.